Airfoil Selection Procedure, Wind Tunnel Experimentation and Implementation of 6DOF Modeling on a Flying Wing Micro Aerial Vehicle

Abstract

Airfoil selection procedure, wind tunnel testing and an implementation of 6-DOF model on flying wing micro aerial vehicle (FWMAV) has been proposed in this research. The selection procedure of airfoil has been developed by considering parameters related to aerodynamic efficiency and flight stability. Airfoil aerodynamic parameters have been calculated using a potential flow solver for ten candidate airfoils. Eppler-387 proved to be the most efficient reflexed airfoil and therefore was selected for fabrication and further flight testing of vehicle. Elevon control surfaces have been designed and evaluated for longitudinal and lateral control. The vehicle was fabricated using hot wire machine with EPP styrofoam of density 50 Kg/ m 3 . Static aerodynamic coefficients were evaluated using wind tunnel tests conducted at cruise velocity of 20 m/s for varying angles of attack. Rate derivatives and elevon control derivatives have also been calculated. Equations of motion for FWMAV have been written in a body axis system yielding a 6-DOF model. It was found during flight tests that vehicle conducted coordinated turns with no appreciable adverse yaw. Since FWMAV was not designed with a vertical stabilizer and rudder control surface, directional stability was therefore augmented through winglets and high wing leading edge sweep. Major problems encountered during flight tests were related to left rolling tendency. The left roll tendency was found inherent to clockwise rotating propeller as ‘P’ factor, gyroscopic precession, torque effect and spiraling slipstream. To achieve successful flights, many actions were required including removal of excessive play from elevon control rods, active actuation of control surfaces, enhanced launch speed during take off, and increased throttle control during initial phase of flight. FWMAV flew many successful stable flights in which intended mission profile was accomplished, thereby validating the proposed airfoil selection procedure, modeling technique and proposed design.

Experimental Investigation of Propeller Induced Flow on Flying Wing Micro Aerial Vehicle for Improved 6DOF Modeling

“…Balance calibration matrix, calibration slopes and interaction constants were evaluated and used to purify results reflected by data acquisition system. The details of complete calibration process along with calibration matrix values are shown in [50]. Since FWMAV was placed over pyramidal balance with the help of a supporting system, therefore, this affects overall drag measured by data acquisition system of subsonic wind tunnel (refer figure 9).…”

“…From the geometrical details of FWMAV, elevons tail volume ratio in elevator role, V H was 0.340, while tail volume ratio for winglets was 0.0411 (refer figure 25). For an estimation of elevon lift curve slope, wing lift curve slope of was used which was determined experimentally through wind tunnel tests [50]. For an estimation of winglets lift curve slope, an inviscid airfoil lift curve slope of 2π was corrected for winglets leading edge sweep of 30 • and aspect ratio of 0.98 as proposed by Helmbold's equation 36, taken from [90].…”

“…Relation of voltage from strain gauge as shown by system with applied load is also shown. Further details on calibration matrix and interaction constants is shown in[50] VI. RESULTS AND DISCUSSIONS The coefficient of lift, C L , was plotted against angle of attack for wind tunnel tests W M 5 − 20, T 3, T 6, T 9, W M 6 − 20, T 12, T 15, T 18, W M 7 − 20, T 21, T 24, T 27 and shown in figure 15.…”

“…Slopes extracted from graph are ∂C L ∂J = −0.879, ∂C D ∂J = −0.192 and ∂C Y ∂J = −0.065. Jana data point is placed for comparison purposes[19] attack of 2 • during wind tunnel testing as shown in[50], therefore aerodynamic forces and moments due to forces were extracted at angle of attack of 2 • and plotted against advance ratios, refer figures 18 and 19. It was noticed that all coefficients of forces decreased with an increase in advance ratio.…”

“…A dihedral angle of 2 • was proposed for lateral stability. Detailed design features of FWMAV is shown in authors' earlier work[50].• pitch attitude which is corresponding to cruise flight of FWMAV. Motor drive, flow conditioning, test section, and control console constitute major parts of subsonic wind tunnel.…”